Instruction manual

Electric Force (EFM) Imaging
Electric Field Gradient Detection—Procedures
Rev. B MultiMode SPM Instruction Manual 259
• Adjust the sample or tip voltage to confirm that contrast is due to electrical force
gradients. On very rough samples, contrast in LiftMode images may be from air
damping between the tip and surface. It is often useful to look at the phase data in Scope
Mode while adjusting the tip or sample voltage up and down. Contrast due to electrical
force gradients should increase or decrease as the tip-sample voltage is changed.
•For more quantitative results, switch the to the frequency Data Type for Channel 1. This
technique provides a direct measure of the change in resonant frequency felt by the
cantilever. It may be necessary to optimize the FM (frequency modulation) gain to
properly track the shifts in resonant frequency. This is described in detail in Chapter 13
of the appropriate product instruction manual.
14.4.2 Amplitude Detection
With Basic Extender Module
To set up for Amplitude Detection field gradient imaging on systems with the Extender module
installed, follow the instructions in Phase Detection: Section 14.4.1, with the exception that the
Channel 1 Data Type should be set to Amplitude.)
Without Basic Extender Module
Note: This imaging method, although described here, is not recommended
without the Basic Extender Module due to the presence of artifacts.
Amplitude Detection, unlike Phase Detection, is available with or without the optional Basic
Extender Module. This section describes the differences in software set up and imaging for EFM
systems without the Extender module. When EFM imaging without the Extender module, changes
in the cantilever amplitude provide an indirect measure of shifts in the cantilever resonance
frequency as shown in Figure 14.4d.
Figure 14.4d Shift in amplitude at fixed Drive Frequency
(Basic Extender Module not installed).
Drive Frequency
Amplitude
∆F
0